The formation of fibers or filaments of various polymers has previously been effected by extruding a molten polymer through spinnerets with the formation of continuous filaments and subsequently chopping such filaments into staple fibers.
Another approach has been to form so-called "fibrids" by introducing a solution of a polymer into a nonsolvent for the polymer under agitation. The formation of such fibrids is described in U.S. Pat. Nos. 2,999,788; 2,988,782; and 2,708,617.
Continuous filaments having a three-dimensional integral plexus structure and called plexifilaments are described in U.S. Pat. Nos. 3,081,519; 3,227,664; and 3,227,784. This process involves flashing a solution of polymer through an orifice under conditions such that substantially all of the solvent flashes off leaving a continuous filamentary structure.
A process of forming microfibers by melting a synthetic polymer and applying a gaseous jet to a thin layer of the molten polymer is described in U.S. Pat. No. 3,016,599.
The production of a continuous, foamed filament by extrusion of a mixture of a blowing agent and a polymer is described in U.S. Pat. Nos. 3,480,507 and 3,542,909.
A process for preparing polyacrylonitrile fibers by extruding a two-phase melt of the polymer in water into a stream of steam is described in U.S. Pat. No. 3,402,231. The fibers are in the form of a loosely constructed, continuous strand. The polymer concentration is less than 30% of the slurry.